As one of safety systems in vehicles, an alarm system which indicates a seat belt non-wearing state when a person gets on the vehicle has been practically used. In this alarm system, a warning is generated when the wearing of the seat belt is not detected in a state where the seating of a person is detected. As a device for detecting the seating of the person, a seating detection device for detecting a load caused by seating is used in some cases.
As the seating detection device, there is known a load detection sensor having a configuration in which a spacer having an opening is disposed between a pair of resinous films and electrodes formed on the films face each other with a predetermined gap interposed therebetween inside the opening of the spacer. However, since the strength of the resinous film generally decreases in accordance with an increase in temperature, there is a tendency that the resinous film is bent by a weak force. Thus, there is a case in which the strength of the resinous film decreases as described above in a high-temperature environment such as a vehicle interior under a hot weather. In this case, even a case in which a load lighter than a normal person's load is applied to the seat device may be erroneously detected as seating.
Patent Literature 1 below discloses a seating detection device capable of suppressing the above-described erroneous detection. In a load detection sensor used in the seating detection device, a spacer having an opening is disposed between a pair of resinous films, electrodes respectively formed on the films face each other with a predetermined gap interposed therebetween inside the opening of the spacer, and a metal plate is disposed on a surface opposite to the spacer on one film to cover the opening.
According to the seating detection device, since the metal plate has elasticity and the elasticity does not change so much depending on the temperature, it is possible to suppress a change in bending of the film at the time of detecting seating with a temperature by the use of the metal plate. Thus, according to the seating sensor, it is possible to suppress a problem in which a load detecting seating changes in accordance with a temperature.
[Patent Literature 1] Japanese Patent No. 5324548